The interaction of dissolved Boom Clay and Gorleben humic substances with selenium oxyanions (selenite and selenate)

Sorption of selenate on soils and pure phases: kinetic parameters and stabilisation

“…The sorption of selenate on bentonite, humic substances and calcium carbonate was not found to be significant for any test conditions. Bruggeman et al (2007) also found no sorption of selenate on argilic humic acid. For humic acid this result is remarkable because it is the solid with the highest elementary Se content (Table 1).…”

Selenium environmental cycling and bioavailability: a structural chemist point of view

“…Thermodynamically, and due to the presence of a reducing phase (FeS 2 ), selenium oxyanions are expected to be reduced to elemental selenium or Se(-II), and to be removed from solution by precipitation (Bruggeman et al 2005). However, in the case of selenate, no speciation change was observed in the experiments of Bruggeman et al (2005Bruggeman et al ( , 2007. This implies that selenate is kinetically inert and that it is meta-stable in groundwaters rich in humic substances in equilibrium with reducing solid phases, and that it may only be reduced by micro-organisms.…”

“…In addition, a newly-formed selenium species was detected, but could not be identified. The authors propose that this new species was associated with the dissolved humic substances (Bruggeman et al 2007). Thus an abiotic route for the transformation of selenite to organically-bound selenium was observed to exist, although the exact nature of this species is not known.…”

“…For this reason, the total cumulative dose of radioactivity could be affected by an eventual release of this radionuclide from waste repositories to the biosphere (ANDRA 2005). This has motivated the study of materials with high selenite retention capacities (the thermodynamically most stable chemical species in these environments), and the study of selenite interaction with clays (Breynaert et al 2008;Bruggeman et al 2007Bruggeman et al , 2005Peak et al 2006), cements (Bonhoure et al 2006;Johnson et al 2000b;Mace et al 2007;Pointeau et al 2006) or clays in the presence of Fe(II) (Charlet et al 2007). 75 Se is another isotope relevant in environmental studies.…”

“…1.2). Bruggeman et al (2007Bruggeman et al ( , 2005 have recently studied the interaction between selenium oxyanions and dissolved humic substances derived from such environments. Thermodynamically, and due to the presence of a reducing phase (FeS 2 ), selenium oxyanions are expected to be reduced to elemental selenium or Se(-II), and to be removed from solution by precipitation (Bruggeman et al 2005).…”